sgl-project/sglang · error · ValueError

cache_salt should be a list or a string.

Error message

cache_salt should be a list or a string.

What it means

Raised when cache_salt is neither None, str, nor list. The normalizer accepts None (skip), a str (broadcast), or a list[str] (per-request); anything else is rejected before dispatch.

Source

Thrown at python/sglang/srt/managers/io_struct.py:816

    def _normalize_cache_salt(self, num):
        """Normalize cache_salt for batch processing."""
        if self.cache_salt is None:
            return
        if isinstance(self.cache_salt, str):
            value = self.cache_salt or None
            self.cache_salt = [value] * num
        elif isinstance(self.cache_salt, list):
            if len(self.cache_salt) != self.batch_size:
                raise ValueError(
                    "The length of cache_salt should be equal to the batch size."
                )
            if any(not isinstance(value, str) for value in self.cache_salt):
                raise ValueError("Every cache_salt should be a string.")
            self.cache_salt = [value or None for value in self.cache_salt]
            self.cache_salt = self.cache_salt * self.parallel_sample_num
        else:
            raise ValueError("cache_salt should be a list or a string.")

    def _normalize_bootstrap_params(self, num):
        """Normalize bootstrap parameters for batch processing."""
        # Normalize bootstrap_host
        if self.bootstrap_host is None:
            self.bootstrap_host = [None] * num
        elif not isinstance(self.bootstrap_host, list):
            self.bootstrap_host = [self.bootstrap_host] * num
        elif isinstance(self.bootstrap_host, list):
            self.bootstrap_host = self.bootstrap_host * self.parallel_sample_num

        # Normalize bootstrap_port
        if self.bootstrap_port is None:
            self.bootstrap_port = [None] * num
        elif not isinstance(self.bootstrap_port, list):
            self.bootstrap_port = [self.bootstrap_port] * num
        elif isinstance(self.bootstrap_port, list):
            self.bootstrap_port = self.bootstrap_port * self.parallel_sample_num

View on GitHub (pinned to 0132848349)

Solutions

1. Use str, list[str], or None
2. Convert tuples: list(tuple)

Example fix

// before
cache_salt=('s1','s2')
// after
cache_salt=['s1','s2']

cache_salt = list(cache_salt) if isinstance(cache_salt, tuple) else cache_salt

def valid_salt(s): return s is None or isinstance(s, (str, list))

When it happens

Trigger: cache_salt=42, cache_salt=('s1','s2') (tuple), or a dict.

Common situations: Passing tuple from an API layer, or numeric salt ids.

Related errors

• Every cache_salt should be a string.
• SGLang currently only supports inferring LoRA target modules
• extra_key should be a list or a string.
• The length of cache_salt should be equal to the batch size.
• Input 'data' must be a torch.Tensor, but got {type(data)}

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/be1278bc5c3fcb8e. Report an issue: GitHub.